Pro-pigmentary action of 5-fluorouracil through the stimulated secretion of CXCL12 by dermal fibroblasts

BACKGROUND: There is growing evidence that 5-fluorouracil (5-FU) combined with therapeutic trauma can effectively induce skin repigmentation in vitiligo patients who are unresponsive to conventional treatments. Previous studies have mainly focused on identifying the antimitotic activity of 5-FU for the treatment of skin cancer, but few studies have investigated its extra-genotoxic actions favoring melanocyte recruitment. METHODS: We utilized the full thickness excisional skin wound model in Dct-LacZ transgenic mice to dynamically assess the migration of melanocytes in the margins of wounds treated with or without 5-FU. The in-situ expression of CXCL12 was examined in the wound beds using immunofluorescence staining. Quantitative real-time polymerase chain reaction and Western blotting analyses were performed to detect the expression levels of CXCL12 mRNA and protein in primary mouse dermal fibroblasts treated with or without 5-FU. Transwell assays and fluorescein isothiocyanate (FITC)-phalloidin staining were used to observe cell migration and filamentous actin (F-actin) changes of melan-a murine melanocytes. RESULTS: Whole mount and cryosection X-gal staining showed that the cell numbers of LacZ-positive melanocytes were much higher in the margins of dorsal and tail skin wounds treated with 5-FU compared with the controls. Meanwhile, CXCL12 immunostaining was significantly increased in the dermal compartment of wounds treated with 5-FU (control vs. 5-FU, 22.47 ± 8.85 vs. 44.69 ± 5.97, P < 0.05). Moreover, 5-FU significantly upregulated the expression levels of CXCL12 mRNA (control vs. 5-FU, 1.00 ± 0.08 vs. 1.54 ± 0.06, P < 0.05) and protein (control vs. 5-FU, 1.00 ± 0.06 vs. 2.93 ± 0.10, P < 0.05) in cultured fibroblasts. Inhibition of the CXCL12/CXCR4 axis suppressed melanocyte migration in vitro using a CXCL12 small interfering RNA (siRNA) or a CXCR4 antagonist (AMD3100). CONCLUSION: 5-FU possesses a pro-pigmentary activity through activation of the CXCL12/CXCR4 axis to drive the chemotactic migration of melanocytes.